> between 70mm and IMAX 70mm.

Im not sure how many vertical 70mm projectors there are left. I don't think its a delivery format any more.

In terms of shooting, I think the only person mad enough to use 65mm is Ken Branagh on his agatha christie movies.

its easier and a fuckload cheaper to shoot anamorphic on 35mm or 35mm digital. Plus I think the choice of scanner is wider.

Thats also another good point, I'm not sure what scanners you can actually use on imax.